SYNOPTIC DESCRIPTION OF THE PHYLUM CHOANOFLAGELLATA

EUKARYA>UNIKONTA>OPISTHOKONTA>ANIMALIA>CHOANOZOA>CHOANOFLAGELLATA

PHYLUM CHOANOFLAGELLATA LNKS

The following information came from Margulis and Schwartz (1998), Barnes (1984), Brusca and Brusca (2003), Lee et al. (1985), Cavalier-Smith (1997), Tudge (2000), and Adl et al. (2005). Because these clearly are not Metazoans, I have used the “protozoan” description format for this phylum.

I. SYNONYMS: The formal taxon Choanomonada was defined by Kent in 1880. Other synonyms include: choanoflagellates, choanomastigotes, choanocytes, collar cells.

II. NUMBER: >140 species known.

III. PHYLUM CHARACTERISTICS:
- A. Structure and Physiology
  - Cell Form: Unicellular to colonial.
  - Flagella: One whiplash flagellum; cells swim with flagellum trailing.
  - Basal Bodies: Microtubular flagellar rootlets radiate from all around the active basal body and terminate beneath the cell membrane without making a connection with the nucleus or the barren orthogonal basal body. The basal body has a central filament in the transition zone.
  - Cell Covering: Base of flagellum surrounded by a ring (collar) of tentacular microvilli (costae) used in filter feeding; some secrete a membranous sheath, a cellulosic lorica (theca), or basket-like lorica of silicaceous bars.
  - Chloroplasts: Sometimes with green plastids.
  - Food Reserves: Not reported.
  - Mitochondria: Flat cristae.
  - Golgi: Present.
  - Nucleus: Uninucleate. Endosome?
  - Centrioles: Not reported.
  - Inclusions and Ejectile Organelles: Food vacuoles and contractile vacuoles.
- B. Reproduction:
  - Mitosis: Not reported.
  - Meiosis: Not reported.
  - Sexual Reproduction and Life History: Not reported; however, a life history with multiple life stages has been reported in Proterospongia.
- C. Ecology: Freshwater to marine; free living, phagotrophic.

LITERATURE CITED

Adl, S. M., A. G. B. Simpson, M. A. Farmer, R. A. Andersen, O. R. Anderson, J. R. Barta, S. S. Bowser, G. Brugerolle, R. A. Fensome, S. Fredericq, T. Y. James, S. Karpov, P. Kugrens, J. Krug, C. E. Lane, L. A. Lewis, J. Lodge, D. H. Lynn, D. G. Mann, R. M. McCourt, L. Mendoza, O. Moestrup, S. E. Mozley-Standridge, T. A. Nerad, C. A. Shearer, A. V. Smirnov, F. W. Spiegel, and M. F. J. R. Taylor. 2005. The new higher level classification of eukaryotes with emphasis on the taxonomy of protists. Journal of Eukaryotic Microbiology. 52(5):399-451. [3,L]

Barnes. R. S. K. 1984a. Kingdom Animalia. IN: R. S. K. Barnes, ed. A Synoptic Classification of Living Organisms. Sinauer Associates, Inc., Sunderland, MA. pp. 129-257.

Brusca, R. C. and G. J. Brusca. 2003. Invertebrates. 2nd Edition. Sinauer Associates. Sunderland, MA. [C,L]

Buck, K. R. 1990. Choanomastigotes (choanoflagellates). In: Margulis, L., J.O. Corliss, M. Melkonian, and D.J. Chapman, eds. 1990. Handbook of the Protoctista; the Structure, Cultivation, Habits and Life Histories of the Eukaryotic Microorganisms and Their Descendants Exclusive of Animals, Plants and Fungi. Jones and Bartlett Publishers. Boston. pp. 194-199. [L]

Cavalier-Smith, T. and E. E. Chao. 1997. Sarcomonad ribosomal RNA sequences, rhizopod phylogeny, and the origin of euglyphid amoebae. Archiv fur Protistenkunde. 147: 227-236.

Cavalier-Smith, T., M. T. E. P. Allsopp, E. E. Chao, N. Boury-Esnault, and J. Vacelet. 1996a. Sponge phylogeny, animal monophyly, and the origin of the nervous system: 18S rRNA evidence. Canadian Journal of Zoology 74:2031-2045. [L]

Lee, J. J., S. H. Hunter, and E. C. Bovee, eds. 1985. An Illustrated Guide to the Protozoa. Society of Protozoologists. Lawrence, Kansas.

Lee, R. E. 1980. Phycology. Cambridge University Press. Cambridge. [C,L]

Margulis, L. and K. Schwartz. 1988. Five kingdoms, an illustrated guide to the phyla of life on earth. 2nd Edition. W.H. Freeman and Co. New York. [C]

Margulis, L. and K. Schwartz. 1998. Five kingdoms, an illustrated guide to the phyla of life on earth. 3rd Edition. W. H. Freeman and Company. New York. [C]

Metschnikoff, E. 1886. Embryologische Studien an Medusen : Ein Beitrag zur Genealogie der Primitive Organe. Atlas Figures 1-12. Alfred Hölder. Vienna. pp. 45-71.

Nielsen, C. 1995. Animal Evolution: Interrelationships of the Living Phyla. 1st Edition. Oxford University Press. Oxford.

Snell, E.A., R.F. Furlong, and P.W.H. Holland. 2001. Hsp70 sequences indicate that choanoflagellates are closely related to animals. Current Biology. 11: 967-970.

Sze, P. 1986. A Biology of the Algae. Wm. C. Brown Publishers. Dubuque, Iowa. [C,L]

Taylor, F. J. R. 1976. Flagellate Phylogeny: A Study in Conflicts. Journal of Protozoology. 23(1):28-40. [C,L]

Tudge, C. 2000. The Variety of Life, A Survey and a Celebration of all the Creatures That Have Ever Lived. Oxford University Press. New York.

Wainright, P. O., G. Hinkle, M. L. Sogin, and S. K. Stickel. 1993. Monophyletic origins of the Metazoa: an evolutionary link with Fungi. Science. 260: 340-342.

By Jack R. Holt and Carlos A. Iudica. Last revised: 02/06/2013

SYNOPTIC DESCRIPTION OF THE PHYLUM CHOANOFLAGELLATA

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